With just a couple of minutes running time, or sometimes after ten or fifteen minutes or so , the air compressor reset button always trips on my air compressor.
If this is your compressor problem here are a few things to look for and perhaps fix if your compressor reset button always trips.
First off, let’s make sure we’re all on the same page and what we are talking about when we are speaking of the compressor reset button.
You might know it as the thermal cut out or thermal safety switch. Others know it as the reset button. You can see one of them on the end of the electric motor in the image below.
It may be a small red button on the shroud of the compressor, it may be a button on the end of the motor if that is visible on your compressor, and I have seen them on the side of the motor at the shaft end, on some compressor motors. Some are inside of the wiring cover on the motor, others are an inline switch on the wiring. The locations of this important piece of equipment on the air compressor sure do vary.
Regardless of where the compressor thermal reset button is on your compressor – on the motor or on the shroud of the compressor – it’s purpose is to cut the power to the motor in the event that the motor itself gets too hot. Without the thermal reset button if there were a condition in the motor that was causing it to get hot, eventually the heat itself would destroy the compressor motor.
If the compressor reset button always trips on your compressor, the motor is getting too hot!
Why A Compressor Reset Button Always Trips – The Power Supply
Check to make sure that your air compressor is plugged right into the wall socket, and it is not being powered through an extension cord or power bar. Reason being is that the wire in the extension or power bar may not be large enough to allow the flow of power that the compressor motor needs.
The power cord of the compressor is sized to allow sufficient power to the compressor motor. Restricting it through a smaller wire will cause the motor to over heat. If the motor overheats, the thermal cut out will shut it down.
Why A Compressor Reset Button Always Trips – Compressor Runs Too Long
If you are using your air compressor for extended periods, more than, say, ten or fifteen minutes at a time, the typicaly DIY air compressor will overheat. The duty cycle of the compressor may be less than the time you are requiring it to run, and the motor will overheat. If you think this is happening to your air compressor, try only running it for ten minutes and then letting it sit for at least that time so the motor can cool, before firing it up again.
Older air compressors – and some not so old if the compressor has tipped over for some reason – can develop a tank check valve leak. If that happens, air will be bleeding out of the tank all the time, even when the compressor is running. If that is happening on your air compressor, it will take much longer for the tank to fill – if it ever does – to cut out, and the by product of that is a motor that overheats.
See the troubleshooting pages on this site about how to fix a leaking tank check valve.
If your air compressor has or is developing a mechanical issue – perhaps a weakened or broken intake or pressure valve or a blown gasket in the pump, the compressor may have to run much longer than normal to fill the tank to cut out. It may run so long that the motor will shut down on thermal cutout before the tank is full. If you air compressor seems to be undergoing this scenario, it may be time to add a valve and gasket kit. The troubleshooting pages on this site address these issues.
If you continue to have problems with your compressor reset button always tripping off, feel free to add a question here, and perhaps I, or one of our many visitors, can help!
Don’t forget the centrifugal switch:
Our thanks to Waite Mccormick for providing the following :
Another issue, the centrifugal switch can stick which will keep the start windings energized tripping the thermal switch within 30 sec.
That centrifugal switch is kinda like 1st gear sorta speaking, and when motor get almost 3/4 of its design r.p.m., it shifts the motor windings to the run windings , kinda like running drive gear. I’ll spare you from the more complicated answer… the start windings are much smaller and can’t withstand the heat (of running full rpm) and results in the kicking of your thermal overload.